PCBs Eating Away at Turtles

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When exposed to certain levels of PCBs, turtles suffer from
stunted growth and weak bones, found a new study.

With low bone-density, turtles have a tougher time diving,
swimming and chewing their food. And the same is probably true
for fish and other wild animals that are exposed to the
ubiquitous environmental pollutant.

It's too soon to know what the results mean for people, and our
level of exposure is probably much lower than what some turtles
experience. But there is reason to believe that the shelled
creatures might be sentinels for human health.

"There have been a few published studies done in Nordic countries
that correlated individuals who consume a lot of fish with
increased incidence of hip fractures," said Dawn Holliday, a
physiological ecologist at Westminster College in Fulton,
Missouri.

"Turtles make and break bone through a very similar process that
mammals and humans do," she added. “If humans were exposed at
similar concentrations, it might be relevant.”

PCBs, which were once commonly used in pesticides and a wide
variety of industrial fluids, have been banned for decades. But
with very slow breakdown times, they are still widespread in the
environment, particularly in more developed areas.

In fish, birds, minks and other creatures, PCBs have been linked
with slower growth rates, particularly in young animals and
developing embryos. Studies have also connected exposure to the
chemical with tumors in mink jaws and deformed heads in
zebrafish. Exposed adult animals tend to suffer from immune
system and related problems.

Holliday and colleague Casey Holliday, who is also her husband,
had previously found that PCB exposure caused the metabolisms of
turtles to slow down, making them sluggish and less able to turn
their food into energy.

To see if turtle bones, too, might be at risk from chemical
exposure, the researchers collected diamondback terrapin eggs
from the wild, hatched them in the lab, and raised them on frozen
brine shrimp.

After eight months to ensure the animals were growing normally,
the scientists injected some of the turtles with a dose of PCB
126 that was equivalent to what they might encounter in an urban
lake or river. Other turtles got a placebo injection.

Six months later, the researchers reported in the journal
Aquatic Toxicology, the shells of the PCB-injected group
had grown just one millimeter (0.04-inch) in length, compared to
10 mm (0.4 inches) in the uncontaminated turtles.

"It was such a big difference that you could see it," Dawn
Holliday said. "You didn't have to get out a ruler to measure
them."

The PCB group also had widespread patches of bone that were not
mineralized, while the pollution-free turtles had strong, hard
bones. Like dioxins and BPA, PCBs seem to interfere with hormone
activity, Holliday said.

The chemicals also appear to disrupt cell growth and
differentiation, said Don Tillitt, an environmental toxicologist
with the United States Geological Survey in Columbia, Missouri.

Linking illnesses and deformations in wild animal with specific
chemicals can be extremely difficult to do, Tillit said. Lab
studies like this one add important details that can eventually
help scientists both solve and prevent environmental mysteries.

"Every time they make progress in better understanding the
adverse effects of chemicals like PCBs, and PCBs in particular,"
he said, "it quite often helps with ecological risk assessments
and how we set regulatory limits for cleaning up sites."

The study is also a reminder that animal deaths aren’t the only
sign that something is wrong in the environment.

"When we see effects like this, we know there are things that are
maybe more insidious," Tillit said. "It's a good reminder that we
have to be on guard."